When a large amount of blood is lost, it is critical to immediately replace the lost volume with a volume expander to maintain circulatory volume, so that the remaining red blood cells can still oxygenate body tissue. In extreme cases, an infusion of real blood or blood substitute may be needed to maintain adequate tissue oxygenation in the affected individual. A blood substitute differs from a simple volume expander in that the blood substitute has the ability to carry oxygen like real blood.
Currently employed blood substitutes use either perfluorocarbons (PFCs) or hemoglobins as the oxygen carrier. PFCs are compounds derived from hydrocarbons by replacing the hydrogen atoms in the hydrocarbons with fluorine atoms. PFCs are capable of dissolving relatively high concentrations of oxygen. However, medical applications require high purity perfluorocarbons. Impurities with nitrogen bonds can be highly toxic. Hydrogen-containing compounds (which can release hydrogen fluoride) and unsaturated compounds must also be excluded. The purification process is complex and costly.
Hemoglobin is the iron-containing oxygen-transport metalloprotein in the red blood cells. Pure hemoglobin separated from red blood cells, however, cannot be used since it causes renal toxicity. Various modifications, such as cross-linking, polymerization, ad encapsulation, are needed to convert hemoglobin into a useful and safe artificial oxygen carrier. The resulting products, often referred to as HBOCs (Hemoglobin Based Oxygen Carriers), are expensive and have a relative short shelf-life.
Therefore, there still exists a need for a lower-cost resuscitation fluid that functions as a volume expander but is also capable of carrying a large amount of oxygen.